Tailored Synthesis of Biogenic Gold and Silver Nanoparticles Using Camellia sinensis Extracts for Enhanced Catalytic Reduction of 4-Nitrophenol

Noble metal nanoparticles, such as gold (AuNPs) and silver (AgNPs) nanoparticles, are valued for their optical, antimicrobial, and catalytic properties, which depend on their size and shape. This study synthesizes gold and silver nanoparticles using aqueous extracts of Camellia sinensis from four tea types (white, black, green, and red) and evaluates their catalytic efficiency in the reduction of 4-nitrophenol to 4-aminophenol. UV-vis spectroscopy confirmed nanoparticle formation, with surface plasmon resonance peaks at 530-534 nm for gold nanoparticles and 427-442 nm for silver nanoparticles, indicating mostly spherical morphologies. Transmission electron microscopy revealed that gold nanoparticles synthesized with white tea had an average diameter of 29.46 +/- 53.92 nm, while silver nanoparticles had an average diameter of 33.11 +/- 18.50 nm. The catalytic evaluation using sodium borohydride as a reducing agent showed a significant correlation between extract composition, nanoparticle size, and catalytic activity (p < 0.05). White tea favored the fastest nanoparticle formation (0.5 hours), while red tea showed the slowest synthesis. Pearson correlation analysis suggests that tea type influences nanoparticle size, morphology, and catalytic performance. This study highlights the potential of Camellia sinensis extracts for the eco-friendly synthesis of nanoparticles with tunable properties for catalytic applications.